An improvement technique for forming a MISFET of a polymetal structure is disclosed in Japanese Unexamined Patent Publication No. Hei 11(1999)-31666. This publication discloses a technology in which the natural oxide formed on the tungsten surface is once reduced, and then, a desirable heat treatment is performed, so that wire tapering and the growth of a needle crystal occurring during the heat treatment due to the reduction treatment is inhibited.
Whereas, Japanese Unexamined Patent Publication No. Hei 11(1999)-26395 discloses the following technology as the measures for relieving the electric field concentration at the gate electrode edge: a gate electrode is formed in a W/WSixNy/WOx structure, and heat treated in a reducing atmosphere, thereby to reduce WOx, and as a result, the gate electrode bottom end is made in a round shape.
Further, Japanese Unexamined Patent Publication No. 2000-331978 discloses the following technology: a W-containing polymetal-structured gate electrode is processed, and then washed with an acidic or alkaline solution substantially not containing hydrogen peroxide, thereby to prevent the dissolution of W.
Other than these, the polymetal gates or metal gates in general are disclosed in, Japanese Unexamined Patent Publication Nos. Sho 60(1985)-89943, Sho 61(1986)-150236, Sho 60(1985)-72229, Sho 59(1984)-10271, Sho 56(1981)-107552, Sho 61(1986)-127123, Sho 61(1986)-127124, Sho 60(1985)-123060, Sho 61(1986)-152076, Sho 61(1986)-267365, Hei 1(1989)-94657, Hei 8(1996)-264531, Hei 3(1991)-119763, and Hei 7(1995)-94716, U.S. Pat. Nos. 4,505,028, 5,719,410, and 5,387,540, IEEE Transaction Electron devices, Vol. 43, No. 11, Nov. 1996, Akasaka et al, p. 1864-1869, Elsevier, Applied Surface Scienece 117/118 (1997) 312-316, Nakajima et al, Nakajima et al, Advanced metalization conference, Japan Session, Tokyo Univ. (1995), and the like.
Further, oxynitriding is disclosed in U.S. Pat. No. 4,282,270, and the like. Still further, the hydrogen exhaust gas treatment is disclosed in U.S. Pat. Nos. 5,202,096 and 5,088,314, Japanese Unexamined Patent Publication Nos. Hei 8(1996)-83772 and 9(1997)-75651, and the like.
Whereas, the matter of the moisture content and oxidation is disclosed in Japanese Unexamined Patent Publication Nos. Hei 7(1995)-321102 and Sho 60(1985)-107840, U.S. Pat. No. 5,693,578, and the like.
Further, the moisture synthesis using a catalyst is disclosed in Japanese Unexamined Patent Publication Nos. Hei 6(1994)-333918, Hei 6(1994)-115903, Hei 5(1993)-152282, Hei 6(1994)-163871, Hei 5(1993)-141871, Hei 5(1993)-144804, and Hei 6(1994)-120206, Nakamura et al, Proceedings of the 45th Symposium on Semiconductors and Integrated circuit Technology, Tokyo Dec. 1-2, 1993, the Electronic materials committee, P. 128-133, and the like.